Photoemission and scanning tunneling microscopy investigation of elemental-semiconductor surfaces
Samsavar, Amin
This item is only available for download by members of the University of Illinois community. Students, faculty, and staff at the U of I may log in with your NetID and password to view the item. If you are trying to access an Illinois-restricted dissertation or thesis, you can request a copy through your library's Inter-Library Loan office or purchase a copy directly from ProQuest.
Permalink
https://hdl.handle.net/2142/20913
Description
Title
Photoemission and scanning tunneling microscopy investigation of elemental-semiconductor surfaces
Author(s)
Samsavar, Amin
Issue Date
1990
Doctoral Committee Chair(s)
Chiang, Tai-Chang
Department of Study
Physics
Discipline
Physics
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Physics, Condensed Matter
Language
eng
Abstract
The clean and reacted surfaces of Si(111)-(7x7), Si(100)-(2x1), Ge(111)-c(2x8), and Ge(100)-(2x1) have been studied to better understand the nature of these elemental-semiconductor surfaces. By carefully monitoring the adsorbate-induced changes in the electronic properties at the surface via spectroscopic methods such as photoemission, and by studying the resulting surface structures by scanning tunneling microscopy (STM), a quantitative description of the interaction and reaction between adsorbate and surface can be obtained. The photoemission method allows a distinction between atoms in different layers and in inequivalent sites by their binding energy shifts. By comparison with structural models and reference samples the number of atoms in each distinct chemical configuration can be determined. An adsorbate-induced chemical shift can be correlated with electronegativity differences between substrate and adsorbate atoms. In particular, studies of noble-metal interfaces with the (100) faces of Si and Ge demonstrate this novel combined application of photoemission and STM.
"The (111) faces of Si and Ge reconstruct to exhibit rather complex chemisorption geometries which are generally not well understood. For clean Si(111)-(7x7), there are three distinct surface sites giving rise to three different chemical environments. To establish the correlation between various surface-shifted components of the core levels and the surface sites, several experiments were designed and performed. The main idea behind these experiments has been to selectively replace atoms or saturate the dangling bonds of a certain surface site by adsorbate atoms, using the noble metal-semiconductor interface as the model system to test this basic approach. Results for other interface systems such as Sb, Sn and NH$\sb3$ with these semiconductors are also presented for comparison. These studies indicate that the ""adatoms"" on the clean Si(111)-(7x7) surface are directly responsible for the metallic surface state in the valence band. Additionally these adatoms exhibit a core level shift of $-$0.77 eV relative to the bulk atoms."
Use this login method if you
don't
have an
@illinois.edu
email address.
(Oops, I do have one)
IDEALS migrated to a new platform on June 23, 2022. If you created
your account prior to this date, you will have to reset your password
using the forgot-password link below.
